Extensible markup language (XML) is increasingly becoming the preferred format for transferring data. XML is a tag-based hierarchical language that is extremely rich in terms of the data that it can be used to represent. For example, XML can be used to represent data spanning the spectrum from semi-structured data (such as one would find in a word-processing document) to generally structured data (such as that which is contained in a table). XML is well-suited for many types of communication including business-to-business and client-to-server communication.
Data represented in XML is often created and retained in electronic documents, such as electronic forms. An electronic form that is written in XML typically is governed by an XML schema (XSD) and can be altered by applying an eXtensible Style-sheet Language Transformation (XSLT) file on the form. For more information on XML, XSLT, and XSD (schemas), the reader is referred to the following documents which are the work of, and available from the W3C (World Wide Web consortium): XML Schema Part 2: Datatypes; XML Schema Part 1: Structures; and XSL Transformations (XSLT) Version 1.0; and XML 1.0 Second Edition Specification.
With so much information being described and transferred through XML, it is increasingly important to have ways to aggregate, or import information from one XML document into another. A manager, for instance, may want to study how his or her salespeople are performing. The manager can study dozens of XML documents, such as purchase orders filled out by the salespeople, and manually order, categorize, and add up the totals to determine how each salesperson is performing. With aggregation, however, the manager can have pertinent data from all of the purchase orders imported into one, summary document. This summary document can be organized to show how much each salesperson sold, when it was sold, and so on. Thus, aggregation can allow people to more easily and efficiently analyze and organize information.
Aggregation, however, can be very difficult to perform. To properly aggregate forms, a programmer commonly needs a thorough understanding of each of the electronic form's schemas. Even with this understanding, the programmer often contends with resulting, aggregated forms that are not valid according to their schemas. These and other complexities typically require a programmer with a high degree of skill to spend a significant amount of time to aggregate data from one electronic form into another.
For these reasons, aggregating XML documents, though useful, can be difficult, time consuming, and require a high degree of skill.